1. Field of the Invention
The present invention relates to electrostatic generators and motors, and more specifically, it relates to passive magnetic bearing configurations.
2. Description of Related Art
(WO/2001/084693) “Full Levitation Bearing System With Improved Passive Radial Magnetic Bearings” The invention provides a full levitation magnetic bearing that uses improved passive radial and axial magnet bearings and an active axial magnetic thrust actuator for axial stabilization. The passive radial magnetic bearings are especially suited for full levitation magnetic bearing systems, because they allows full levitation support with simple, low cost single axis active control. The bearings use multiple axially magnetized, concentric magnet rings or, alternatively in another embodiment, concentric magnetized ring portions of a single block of magnetic material attached to the stationary portion, cooperating with pole rings on the axial face of a ferromagnetic rotating portion. This cooperation creates both an axial attractive force and passive radial centering forces, as the pole rings tend to align with the stationary permanent magnet rings. In a preferred embodiment, the concentric permanent magnet rings are arranged with alternating axial polarities for generation of maximum radial stiffness.
'693 is directed to a magnetic bearing that is a simple combination of passive magnetic bearing elements that are stable against radial displacements plus active stabilization means for axial displacements (which are otherwise unstable).
U.S. Pat. No. 5,847,480, titled: “Passive magnetic bearing element with minimal power losses”, is directed to systems employing passive magnetic bearing elements having minimal power losses are provided. Improved stabilizing elements are shown, employing periodic magnet arrays and inductively loaded circuits, but with improved characteristics compared to the elements disclosed in U.S. Pat. No. 5,495,221 entitled “Dynamically Stable Magnetic Suspension/Bearing System.” The improvements relate to increasing the magnitude of the force derivative, while at the same time reducing the power dissipated during the normal operation of the bearing system, to provide a passive bearing system that has virtually no losses under equilibrium conditions, that is, when the supported system is not subject to any accelerations except those of gravity. '480 uses a combination of radially stable passive bearings together with a null-type induction-driven passive magnetic bearing element that providces axial stabilization characterized by very small power losses at equilibrium.
U.S. Pat. No. 7,023,117, titled: “Magnetic bearing arrangement” is direct to a magnetic bearing arrangement (1) for a motion element, having the following features: the magnetic bearing arrangement has a stator. The magnetic bearing arrangement has a passive magnetic bearing (3, 8, 9) for lateral guidance of the motion element (2) and a controllable magnetic bearing (3, 5) for guidance of the motion element perpendicular to the guidance by way of the passive magnetic bearing. The controllable magnetic bearing has an electronic stabilization device; the stabilization device has an electrical conductor (6, 7) that can have an electrical control current applied to it by the stabilization device and that is associated with the stator element (5) in such a way that the magnetization of the stator element is influenced by the control current. The controllable magnetic bearing has a permanent magnet (3); the permanent magnet is arranged on the motion element opposite the stator element. The magnetic force between permanent magnet and stator element is dimensioned such that with a control current of zero, the motion element is held in the working position; and only upon deviation from that working position is a control current generated that influences the magnetization of the stator element in the direction of re-establishing the working position. '117 pertains to a radially stable passive bearing similar to Gabrys', also with y means for axial stabilization employing electron feedback.
All three of the cited patents employ elements that are radially stable but axially unstable. In the work to date at Lawrence Livermore National Laboratory (LLNL) on passive magnetic bearings, the approach has been to achieve stability, in this case only in the rotating state, by using rotating Halbach arrays to generate currents in stationary “stabilizer” element windings. These currents, interacting back on the Halbach array fields, then produce strong centering forces, thereby overcoming the strictures of Earnshaw's Theorem. The stabilizer, however, also introduces some parasitic losses and is still somewhat complex.
A passive magnetic bearing is desirable that is stable against axial displacements and that enables a radial stabilizing force that approaches zero when the system is centered, where the amount of stabilizing force required is small and the drag forces exerted will be small. The present invention fulfils such a desire.